M42 and T 2 mounts

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David Frydman
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Joined: Mon Jan 18, 2010 9:25 am

M42 and T 2 mounts

Post by David Frydman »

Frequently these 2 metric measure mounts seem to get mixed up.

Although the following is from internet sources and my own experience I think it is accurate.

The M42 mount is from cameras with a flange distance of 45.5 or 45.46mm.
It originted with Practica, Pentacon and Pentax although may be earlier.

M42 lenses should be interchangable and fit all M42 bodies but they are not. The actuating pin length varies and some lenses don't work on all bodies.
On some cameras they can even jam and only a camera repair person can get them apart.

The important thing is that the M 42 thread pitch is 1 mm.

The T 2 thread is different it is 0.75 mm.

This comes I think from Tamron, although I don't off hand know the distance between the register of the T 2 mount.

These T 2 mounts come in many fittings.
They are composed of the rear part with a bayonet or indeed thread that fits a camera.
The front is a removable ring sometimes with a channel on the outer part.
This is usually held in by three small grommet? screws to the rear part of the T 2 adapter.

Internally this ring has a T 2 thread of 42mm and 0.75 mm pitch.

It may be that even the profile of M 42 and T 2 threads are different.

If you mix these up and have a valuable DSLR body on the wrong mount you could smash the camera if it falls off and lose £500 plus.

The T 2 mount is rather incorrectly often called a T mount.

There are other T mounts.

T4 used I think by Vivitar.
Also TX also I think Vivitar.

Some lenses such as the large MTO Soviet/Russian mirror lens of 1000mm or 1100 mm focus seem to use just the outer part of a T 2 mount directly attached to the lens without the ring.

There are also from Memory H mounts which are a bit different.

And the Miranda screw thread was 44mm.

There are hundreds of different camera and lens mounts.

But the main thing to note here is that M 42 and T 2 or so called T mount threads are not the same.

Regards, David
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Post by dazcaz »

Tamron made the Adaptall system of lenses that, in theory, could fit any camera just by changing the adapter to one that suits your body.

They are responsible for the T2 or T-mount adapters.

As you say the pitch is different to that on the M42 lenses. This is annoying, but it was probably a way of making money. If the pitch was the same as M42 lenses then the T2 mounts would have sold in their millions and people would not have gone out and bought Tamron lenses, they would have just bought the adapter and screwed it to their M42 lenses. Quite clever really :)

The pins on M42 lenses did vary. IIRC Zenit(h) lenses would fit on Praktica bodies but not the other way around... This might be arse backwards, it's so long ago I forget :)
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David Frydman
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Joined: Mon Jan 18, 2010 9:25 am

Post by David Frydman »

Here I have a new Jessops Made in Korea T 2 Adapter for Nikon and
T 2 Mount adapter for M 42 Made in Japan new but old and anonymous.

When you screw the M 42 mount into the internal T 2 thread of the Nikon T 2 adapter it screws in 1.4 turns before it locks.
This is enough to be of concern, as if someone assumes they have the right adapter one really could have a camera or other item fall off and smash.

The H adapter that I also had somewhere is even more confusing.

Incidentally, Opticron currently sell direct or through dealers their own name T 2 mounts that are still Made in Japan.
I cannot guarantee you would get a Japanese adapter, but I have got these recently and over the past two years. They are sealed in Opticron packs.
I much prefer these to the generally available Korean or Chinese versions.
I think Japanese quality and quality control is better.
The Opticron T 2 mounts are not more expensive than other branded versions.

I have had a beautiful camera get smashed while trying to photograph comet Kohoutek.
Not because of a T 2 mount mix up but nonetheless I was heartbroken.

So please avoid a repeat of this.

Regards, David
David Frydman
Posts: 5366
Joined: Mon Jan 18, 2010 9:25 am

Post by David Frydman »

In addition to the above there are reverse ring adapters allowing many camera lenses to be reversed by using the filter thread plus the adapter.
This is for close up and works very well.

These include reversing M 42 lenses, so one should be careful not to assume the 42mm here is a T 2 thread.

Also it is possible to use say a 135mm lens and attach a reversed 50mm lens to give good results using the filter threads with adapters.

Further, the filter threads on camera lenses have either 0.5mm, 0.75mm or 1.0mm threads.
Luckily 42mm is not usually found although 43mm is common.

However Cokin A filters do have a 42mm adapter although I don't know what pitch this is.

M 42 lens adapters exist for several cameras such as Minolta.
These are usually stainless steel and much thinner than a T 2 adapter.
They are thin to preserve infinity focus.
Be sure to get the key with them so you can unlock this thin ring.
Without it you may have a problem getting it off the camera body.

Regards, David
David Frydman
Posts: 5366
Joined: Mon Jan 18, 2010 9:25 am

Post by David Frydman »


It seems there may be a difference between the T 2 and T mount descriptions.

The T 2 refers to the camera to lens adapters that contain an inner rotatable ring and a separate back outer part.

The T mount may be a one part adapter without the separate inner ring.

There is also the Sigma YS system which is a complicated T 2 mount with various alternatives for coupling to camera metering systems.

The Vivitar/ ? Soligor T 4 and TX were also complicated systems.

I find the various versions of the Tamron Adaptall system also difficult.

To me the wonderfully simple T 2 mount is much easier.

As an aside I had Soligor 135mm f/1.8 and 135mm f/2 lenses with T 2 mounts.
The full aperture performance of the f/1.8 was much worse than the f/2.
There was also a Soligor 135mm f/1.5 and I think Vivitar 135mm f/1.5.
I have seen these in the U.S. but not here.

Also even the Soligor 135mm f/2 had much worse contrast than say a Minolta or Nikon 135mm f/2.
But they cost much less and the Soligor was all I could afford.

Sigma made a wonderful early 200mm f/3.5 or f/4 ? lens.
I think it was called something like an SQ I cannot remember.

What was remarkable was that it had a normal focussing mount but had an additional function where the front lens group could be rotated very quickly giving 1 to 1 Macro in an instant.
And it worked, I liked it a lot, but I think it was not successful.
It should have been.

David Frydman
Posts: 5366
Joined: Mon Jan 18, 2010 9:25 am

Post by David Frydman »

Just talked to a friend and I said luckily there are no 42mm camera lens filter sizes.
Oh No.
Contaxes from 1932 onwards with at least 4 different Zeiss focal length lenses had 42mm filter threads. The 50mm f/2 Sonnar I think was the only 50mm.

Also large format cameras using top quality Schneider lenses used and maybe still use 42mm threads.

I said filter threads are in 0.5mm, 0.75mm and 1mm pitch.
He said the ones you normally meet are 0.75mm.
Now this is the T. mount size.

Then I found out that there was a T 1 adapter which had a different size inner ring to the popular T 2.
And we now have just the T mount.

The metric size threads have a 60 degree included angle thread profile with a slightly rounded top.

The Leica 39mm lens mount is NOT metric it uses a pitch of 26 threads per inch not 25.4.

The Soviet lenses are different and original Canon 39mm lenses were one thing but changed to Leica standard.

An amazing conversation on the complexities of threads.

Also metric bolts have at least three pitches. Fine, Standard and Coarse.


Regards, David

Also the original Nikon rangefinder 50mm f/1.5 lens apparently had a 42mm filter thread.
When they went to a 50mm f/1.4 lens the filter thread changed to 43mm.
Generally Japanese lenses went to 43mm. Many of the Nikon rangefinder lenses are 43mm filter thread.
Nowadays you do not commonly see a 42mm filter thread filter or accessory.

The German lenses may have kept some 42mm filter thread lenses.
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